I would try a hydrogen peroxide dip for 5 minutes. They may not open for a week after but I have had 2 colonies that never seem to open all the way or only open for short periods of time a per day. Dipped them in peroxide and about 5 days later they began to open up more, by day 10 after the dip they seemed completely normal. Zoas can also take a while to acclimate sometimes. Be cautious dosing iodine, overdoing can be bad from what I have read. I dose iodine but only started dosing after an icp test determined my tank was deficient. I only dose half of the recommended dose as I would rather be on the low side of safe then overdosing.